1. Field
The present disclosure relates to a method for preparing nickel-aluminum alloy powder at low temperature, more particularly to a method for preparing nickel-aluminum alloy powder at low temperature by adding aluminum chloride as a reaction accelerator to a powder mixture of nickel powder and aluminum powder and carrying out reaction in vacuum, thus preventing inter-particle aggregation and avoiding the need of pulverization without requiring supply of high-purity hydrogen for the purpose of preventing oxidation.
2. Description of the Related Art
Nickel-aluminum alloy is an inter-metal compound whose use in high-temperature applications is expected. Recently, the material is put to practical use as high-temperature parts for heat treatment, die materials for forging and die materials for die casting.
In particular, applicability as hydrogen-generating catalyst, for example, in fuel cells have been proposed and the applications of the inter-metal compound as catalyst are being extended (Science, 300(27), 2075-2077, 2003).
In the general method for preparing nickel-aluminum alloy, since nickel and aluminum particles are molten and mixed to form a solid solution, heat treatment at high temperature of 1400° C. or above is necessary. Further, the heat treatment has to be performed under high-purity hydrogen atmosphere to prevent oxidation of nickel and aluminum.
In the existing general method, the alloy is obtained in the form of aggregate due to inter-particle sintering because the preparation is carried out at high temperature. Accordingly, the nickel-aluminum alloy aggregate needs to be pulverized into particles for use in catalysts, electrodes or other applications. Hence, an additional pulverization process is required for the preparation of nickel-aluminum alloy particles. These factors contribute to increased price of nickel-aluminum alloy powder.
The inventors of the present disclosure have proposed a method for manufacturing a nickel-aluminum inter-metal compound for fuel cells using aluminum chloride (AlCl3). According to the method, it is possible to prepare a nickel-aluminum inter-metal compound below the melting points of nickel (Ni) and aluminum (Al) (U.S. Pat. No. 6,893,481; Korean Patent No. 10-0480830).
Although this method significantly lowers the temperature at which the nickel-aluminum alloy is prepared, the prepared nickel-aluminum particles are obtained in aggregate form and an additional pulverization process is necessary.
In addition, expensive high-purity hydrogen has to be flown continuously during heat treatment to prevent oxidation of nickel and aluminum. Furthermore, it is necessary to continuously supply aluminum chloride (AlCl3) vapor in order to promote it is reaction at low temperature. Since aluminum chloride (AlCl3) is highly corrosive, it may corrode the pipeline, electric furnace or the like, thereby reducing the life span of equipments or utilities.
In order to solve these problems, the inventors of the present disclosure propose a method for preparing nickel-aluminum alloy powder at low temperature by adding aluminum chloride as a reaction accelerator to a powder mixture of nickel powder and aluminum powder and carrying out reaction in vacuum, thus preventing inter-particle aggregation.